pathology of rashes Flashcards
what are functions of the skin
- strong barrier to antigens and organisms
- thermoregulation-BV and sweat glands
- fluid and electrolyte balance-sweat glands
- endocrine function-UV stimulation of vitamin D
- Protein from UV rays-melanin pigment
- immune function langerhans cells
- sensory function-touch, temperature, pressure
what is the structure of the normal epidermis
Epidermis = stratified keratinising squamous epithelium
- prickle cell - prominent desmosomes
- granular layer - rich in keratohyalin granules
- corneal layer - differentiated keratinised cells
- corneocytes - shed from surface - house dust
- melanocytes found in basal layer
- langerhans cells found in upper and mid epidermis
what does papillomatosis mean
irregular epithelial thickening
what does spongiosis mean
oedema fluid between squares appears to increase prominence of intracellular prickles . If severe vesicles filled by oedema fluid developed
how do you classify of inflammatory skin diseases
4 main reaction patterns
- spongiotic intraepidermal oedema eg eczema
- psoriasiform-elongation of the rate ridges eg psoriasis
- lichenoid basal layer damage eg lichen planus
- vesiculobullous-blnstering eg pemphigoid
what os the pathogenesis of psoriasis
- epidermal hyperplasia increase epidermal turnover
- new lesions can arise at sites of trauma (Koebner phenomenon)
- complement mediated attack on keratin later - complement attracts neutrophils to keratin layer
what is auspitz sign
the appearance of small bleeding points after successive layers of scale have been removed from the surface of psoriatic papules or plaques.
what are lichenoid disorders
- conditions characterised by damage to basal epidermis
- prototypic condition is lichen planus - common
- itchy flat topped vioalceous papule
what is lichen plantus histology
- irregular sawtooth acanthosis
- hypergranulosis and orthohyperkeratosis
- band like upper dermal infiltrate of lymphocytes
- basal savage with formation of cymoid bodies
what are immunobullous disorders
blistering cutaneous disorders that are caused by pathogenic antibodies binding to protein targets within the skin. Vesicles and bull occur as secondary phenomenon in many skin diseases
what is pemphigus vulgaris
- autoimmune condition
- IgG auto-antibodies made against desmoglein 3 (maintains desmosomal attachments)
- immune complexes form on cell surface
- complement activation (causes inflammatory cells to move under the skin) and protease release
- disruption of desomsomes
- end result is pacantholysis
what os dermatitis herpetiformis
- autoimmune bullous disease
- strong association with coeliac disease
- associated with HLA-DQ2 haplotype
- intensely itchy lesions - symmetrical
- elbows, knees and buttocks - often excoriated
- hallmark is papillary dermal micro abscesses
- IgA deposits in dermal papillae
what is the aetiology of acne vulgaris
Distribution reflects sebaceous gland sites: face, upper back, anterior chest
- increase in androgens at puberty
- increase androgen sensitivity of sebaceous glands
- keratin plugging of pilosebaceous units
- infection with anaerobic bacterium corynebacterium acnes
how does acne form
- sebum produced by sebaceous gland plugs polo sebaceous unit
- keratin and sebum build up to produce comedones (black/white heads)
- rupture causes acute inflammation and foreign body granulomas
what is the pathology of rosacea
- vascular ectasia (blood vessels on surface)
- patchy inflammation with plasma cells
- pustules
- perifollicular granulomas
- follicular Demodex mites often noted
